I am not suprised that an Arch Linux based distro is the winner on this tests, followed by a Gentoo based very near. They both tries to be as simple as possible.
I use Arch Linux as my first distro choise, and Debian in second place.
Read below, to see the results of the test, and go to the original info, to see the graphs.

Amplify’d from jeffhoogland.blogspot.com

Best Linux Distro for 3D Performance

The Hardware: While my hardware is not fastest in the world it is decently quick. Processor - Intel p9700 2.8ghz Dual Core, RAM - 4gigs of DDR3 1066, Video Card: nVidia 260m with 1gig DDR3 dedicated memory (Running the latest stable nVidia driver 256.53).

The Software: I used my favorite OpenGL benchmarks made by Unigine Company. The distros I am going to compare are: Ubuntu 10.04 (Pinguy) - Gnome Ubuntu 10.10 Beta - Gnome Linux Mint Rolling Release (Debian Based) - Gnome Chakra 0.2.1 (Arch Linux Based) - KDE Fedora 13 - Gnome Mandriva 2010.1 - KDE OpenSUSE 11.3 - KDE PCLinuxOS 2010.07 - KDE Sabayon 5.3 (Gentoo Based) - KDE

Across all three tests Chakra scored the highest (With PCLinuxOS and Sabayon in close second and third). Ubuntu 10.04 was at the very bottom (over 10% behind Chakra). While I think Ubuntu is a great distro it appears that if you are a Linux Gamer, you are better off using a non-Ubuntu distro.Read more at jeffhoogland.blogspot.com

As the author admits, this are just his data using his hardware and configuration.
But the results shows that Linux is improving comparing to the first results he had.
Anyway, it may be a good idea that someone try to do a more in dept test about this comparison

Amplify’d from jeffhoogland.blogspot.com

Linux Out Performs Windows in OpenGL

Using the Unigine benchmarks Windows 7 on my system obtains the following average frames per second:

Tropics - 30.5 FPS Sanctuary - 35.2 FPS

Of all the Linux distros I recently tested, Chakra Linux performs the best in these benchmarks with the following average frames per second: Tropics - 38.0 FPS Sanctuary - 38.3 FPSRead more at jeffhoogland.blogspot.com